1. Field
Embodiments of the present invention generally relate to a magnetic recording system, and a magnetic recording device fitted with a magnetic head and a magnetic recording medium, employing said magnetic recording system.
2. Description of the Related Art
The heart of a computer is a magnetic disk drive which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider towards the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
Through the years, the amount of data that can be stored (i.e., the recording density) on the magnetic disk drive has increased. The bit direction and track width direction of recorded magnetized information are both reduced in order to increase the recording density in a magnetic disk device. To this end, the cluster size of the recording medium has to be refined and the recording head field has to be made steeper. The more refined the cluster size becomes, the greater the deterioration in the value of (KuV/k T), which is an indicator of thermal stability in the reversal region, where Ku is the magnetic anisotropy constant, V is the magnetization minimum unit volume, k is the Boltzmann constant, and T is the absolute temperature. It is necessary to increase the anisotropy magnetic field Hk as a means for solving this problem. The higher the value of Hk, the greater the field intensity has to be. In the case of high-density recording, the recording track width also has to be reduced, which leads to a subsequent problem in that the recording field is inadequate.
A method for alleviating this problem has been proposed in which the recording medium is locally heated only during recording in order to reduce the effective coercive force Hc. This method is widely called heat-assisted recording, and a method in which heating is provided by light in particular is referred to as heat-assisted magnetic recording (HAMR). Microwave-assisted magnetic recording (MAMR), in which the switching field of a medium is reduced using microwaves, has also been proposed.
Furthermore, shingled magnetic recording (SMR) which involves overwriting one side of a recording track has also previously been proposed. In SMR, recording tracks which are recorded on the magnetic recording medium by means of a magnetic head are recorded in a partially overlapping manner. SMR involves recording in such a way that recording tracks are overlapping, as shown in FIG. 1A-1C. A track Tw 1 is first of all recorded (See FIG. 1A), and a track Tw2 is then recorded in such a way as to partially overlap the track Tw 1 (See FIG. 1B). A track Tw3 is recorded in the same way (See FIG. 1C). It is possible to realize a magnetic recording device having a track pitch which is smaller than the recording tracks to be recorded. It is also feasible to use an arrangement in which the magnetic pole width of the recording head is greater than that of a conventional perpendicular magnetic recording device. Furthermore, one side is overwritten, and therefore there are fewer constraints as to the shape of the magnetic pole over the width thereof, and it is possible to increase the field intensity and gradient.
However, the requirement of increased recording volume has not kept up with the current increase in data volume. It is therefore necessary to increase the recording density in SMR. To this end, it is necessary to provide a field distribution which is suitable for SMR.
Therefore, there is a need in the art for a magnetic recording system for SMR which makes it possible to produce a large field intensity and field gradient, and a field distribution which is suited to higher density.